CI: Update Cygwin build to Python 3.7

.github/workflows/cygwin_build.yml

@@ -15,8 +15,8 @@ jobs:
           HOME: ${{ runner.workspace }}/ardupilot
         run: |
           choco install cygwin --params "/InstallDir:C:\Cygwin /NoStartMenu /NoAdmin"
-          choco install cygwin32-gcc-g++ python36 python36-future python36-lxml python36-pip python36-setuptools python36-wheel git libexpat procps gettext --source cygwin
-          C:\Cygwin\bin\bash --login -c "ln -sf /usr/bin/python3.6 /usr/bin/python && ln -sf /usr/bin/pip3.6 /usr/bin/pip"
+          choco install cygwin32-gcc-g++ python37 python37-future python37-lxml python37-pip python37-setuptools python37-wheel git libexpat procps gettext --source cygwin
+          C:\Cygwin\bin\bash --login -c "ln -sf /usr/bin/python3.7 /usr/bin/python && ln -sf /usr/bin/pip3.7 /usr/bin/pip"
       - name: Build SITL
         env:
           HOME: ${{ runner.workspace }}/ardupilot